The physical downsizing of microprocessor based technologies has led to portable personal computers, pocket secretaries, wireless phones and pagers. All of these devices, and also other devices such as clocks, watches, calculators, etc., have the common need for a low power consumption data display screen to extend the useful working time between battery replacements or battery charges.
The common Liquid Crystal Display (LCD) is often used as the display for such devices. LCDs can be classified based upon tile source of illumination. Reflective displays are illuminated by ambient light that enters the display from the front. In applications where the intensity of ambient light is insufficient for viewing, supplemental lighting, such as a backlight assembly, is used to illuminate the display. Some electronic displays have been designed to use ambient light when available and backlighting only when necessary. This dual function of reflection and transmission leads to the designation, "transflective".
A limiting feature of all three types of the above described conventional LC displays are the dichroic polarizers conventionally used on both the front side and the rear of the LCD) panel. These polarizers most commonly use a dichroic dyed, oriented polymer polarizer that strongly absorbs one polarization of light (&gt;99%) and weakly absorbs the other polarization (5-20%). Liquid crystal displays use two sheets of this type of polarizer combined with a liquid crystal panel to selectively allow transmission of light. The absorption by the dichroic polarizers greatly reduces the brightness and contrast in both reflective and backlit displays.
Another drawback to convention LCDs is that the reflector placed behind the backlight assembly are typically only about 94-96% reflective. In other words, these reflectors absorb between 4-6% of tile light at each reflection. Given that light may experience several reflections before exiting the backlight cavity, this amount of absorbance leads to decreased display efficiency, brightness and contrast.
Thus, there is a need in the art for polarizers and reflectors which are more efficient, have higher reflectivity and better performance, and are thus able to contribute to enhanced display efficiency, brightness and contrast.